1. Field
The present invention relates generally to radiation imaging, and more particularly to systems used to acquire radiation images.
2. Description
Conventional radiation treatment typically involves directing a radiation beam at a tumor in a patient to deliver a predetermined dose of treatment radiation to the tumor according to an established treatment plan. A suitable radiation treatment device is described in U.S. Pat. No. 5,668,847, issued Sep. 16, 1997 to Hernandez, the contents of which are incorporated herein for all purposes.
Healthy tissue and organs are often in the treatment path of the radiation beam during radiation treatment. The healthy tissue and organs must be taken into account when delivering a dose of radiation to the tumor, thereby complicating determination of the treatment plan. Specifically, the plan must strike a balance between the need to minimize damage to healthy tissue and organs and the need to ensure that the tumor receives an adequately high dose of radiation. In this regard, cure rates for many tumors are a sensitive function of the radiation dose they receive.
Treatment plans are therefore designed to maximize radiation delivered to a target while minimizing radiation delivered to healthy tissue. If the radiation is not delivered exactly as required by the treatment plan, the goals of maximizing target radiation and minimizing healthy tissue radiation may not be achieved. More specifically, errors in radiation delivery can result in low irradiation of tumors and high irradiation of sensitive healthy tissue. The potential for mis-irradiation increases with increased delivery errors.
Many types of systems have been developed to ensure that radiation will be delivered to a proper area and with the proper dosage. For example, a light field is often used to indicate the position of a field within which radiation will be delivered. Accordingly, these systems rely on various techniques to ensure that the light field and the field of actually-delivered radiation are congruent. Some of these techniques verify the congruence using images obtained by portal imaging devices.
Modern radiation therapy uses beam-shaping devices to produce radiation fields of various shapes. These radiation fields may be used to provide more precise treatment than otherwise available. In order to avoid irradiation of unintended targets by a shaped radiation field, an operator verifies that the beam-shaping devices are configured so as to produce a field shape that complies with a specified treatment plan. As described above, this verification often includes the comparison and manipulation of images obtained by a portal imaging device.
In addition, the accuracy of some techniques for verifying an applied radiation dosage increases with the sensitivity to radiation of an imaging device that is used in conjunction with the techniques. Accordingly, it would therefore be beneficial to provide a radiation imaging system that may offer more efficient and accurate verification of field congruence, field shape, and/or radiation dosage. When used in conjunction with conventionally-designed treatments, such a system could reduce the chance of harming healthy tissue. Such system may therefore also allow the use of more aggressive treatments than currently available.